1. Field of the Invention
The invention generally relates to micro electromechanical systems (MEMS), and more particularly to fracture testing, reliability testing, and fatigue testing of MEMS.
2. Description of the Related Art
Micromachined devices are typically tested individually using force probes which measure the strain on cantilever beams or other beam-type devices. This type of individual testing is quite time consuming and requires sophisticated equipment to measure strains and forces. Some wafer-scale fracture tests have been proposed whereby electrostatic forces between fixed and moving pieces are used to move the device to failure. These methods have the potential to test multiple devices in sequence or possibly in parallel (i.e., simultaneously) if the number of data channels is sufficient. For example, U.S. Pat. No. 5,528,151 issued to Perez, the complete disclosure of which, in its entirety, is herein incorporated by reference, teaches thermal fatigue testing using several test strips anchored to a base.
Nonetheless, electrostatic actuation requires knowledge of the electrical-mechanical interface to convert voltage into mechanical displacement. This causes some uncertainty in measurement. Most prior attempts using electrostatic actuation have generally failed to achieve large enough forces to actually fracture a device. Therefore, there remains a need for wafer-scale or batch testing techniques, which achieves greater measurement accuracy and certainty.